49Issue 02 | 2010

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Know what‘s going on - The use of web based monitoring and analysis-based platforms for the monitoring of slopes in opencast mines and quarries

Slope failure usually occurs when the shear strength of the in-situ material is weakened by one or more factors (e.g. geometrical, geological and hydrological conditions), or when external driving forces are greater than the internal holding forces. In hard rock, stability problems are mainly due to sliding on predetermined slip-surfaces. Besides sliding there is also the possibility of tipping to be considered. The zones of weakness are formed by the existing fracture system in the rock mass. Besides classical slope failures there is a danger of liquefaction in water-saturated areas, the sudden transition from a solid to a liquefied state. The structural collapse, for example of an embankment with its base submerged in water, usually causes the failure of the entire overlying dry slope. The resulting rapid momentum is acutely life-threatening. In the past, this has resulted in more than a dozen fatal accidents in the lignite mining industry, but risks are present in non-metallic minerals mining too. Particularly vulnerable are areas where non-usebale fine sediments are dumped back in the pit during the wet-extraction process. Due to their particle size distribution, the loose density and degree of water saturation, they are at particular risk for liquefaction events.

Rehabilitation can be carried out on unstable slopes by making changes to the geometry (flattening and setting up berms), cut at the top of the slope; fill at the base or by technological

by Thomas Graf, Timothy D. FyfeFUGRO CONSULT GmbH | Berlin | Germany

These days, ensuring the technical and operational safety requirements, is one of the core activities in the operation of quarries and open pit mines. Especially, the geotechnical stability of slopes during open pit operations contains a considerable risk potential.

or biological supporting measures. Rehabilitation is usually very complex, costly, and can only be partially implemented during ongoing open pit operation. Hence, for reliable monitoring of slopes in opencast mines the use of advanced monitoring systems is recommended. In the short term this can quickly provide answers to questions like: Where is the groundwater in the slope? Are slope movements occuring? Which precautions must be taken? In the past, such issues could only be resolved by using time consuming field measurements, monitoring and evaluation campaigns. The results of such measurements usually came too late, as many past accidents show.

Fig. 1: Laser tachometer for slope monitoring

50Issue 02 | 2010

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Today modern internet-based applications can ease this situation. Within a short space of time, automated answers to the questions posted above can be delivered in real-time. Such systems ensure that all the relevant parameters and their trends can be quickly visualised and analysed graphically.

Web-based systems transform data from sensors and measuring points in the field into concise visual information. Data from various devices and sensors, such as total stations, inclinometers, extensometers, piezometers, GPS, webcams, borehole sensors, meteorological instruments, etc. can be collected and retrieved in real time from anywhere in the world.

In recent years FUGRO CONSULT GMBH has developed the GeODin software platform into an automated system for managing data of a pre-installed monitoring network, which has been successfully employed in several complex slope and hillside monitoring projects.

In simple terms such systems work as follows: In a typical surveillance area any number of sensors will be installed. The sensors measure pre-defined parameters at regular intervals and produce files in ASCII format. These files are transferred to a locally installed PC in the field.

The files on the field PC are copied at regular intervals to an FTP server and for data security also stored as zip archives on the PC in the field. The data is then collected from an FTP server and after passing a series of „Thresholds“ tests automatically written to various tables in a database. If necessary, and depending on the actual values measured, both pre- & post-processing can

Fig. 2: Screenshot of a web based monitoring

system with different sensor types

51Issue 02 | 2010

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be carried out on the original data to produce additional virtual parameters that can be stored in the database too.

The GeODin Portal Server presents this data by creating a series of interlinked web-pages in real time on the basis of the information currently available in the database. The web pages are GeODin layouts produced „on-the-fly“ and viewable in any web browser. The individual web pages can contain a wide range of graphic types (tables, lists, time-series, trend lines, XY plots, variable text elements etc.), as well as images (photos, logos) all of which can be interlinked within the portal and to map server applications.

The GeODin platform enables the creation of complete web portals to present your data. This can be done without knowledge of HTML programming or web design. Furthermore, you can extend the functionality of the GeODin Portal Server through the use of other server-side (PHP, ASP) or client-side (JavaScript) technologies.

In addition, a function for ad-hoc creation of reports in PDF format is included.

For example, visitors to your web portal can be provided with the complete documentation of a borehole. This can be spread over several individual layouts such as a header page, a summary log and a well design profile as well as providing a link to download the complete report on the borehole on this hole as a PDF file. An important safety feature is the ability to run the database scripts that control the alarm functions. These critical parameters can be freely defined and you can also specify which events trigger what kind of alarm (a text message and / or an e-mail) to be sent to specific persons responsible. The sending of periodic reports to selected recipients is also included.

It is important that these systems can be customised to the individual needs of mining operations. Their usefulness demands that they provide a generic solution, universally adaptable, without restrictions and easily expandable for

Fig. 3: Sample layout for data presentation

52Issue 02 | 2010

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the future. Of course, with all the configuration possibilities and 24/7 accessibility, the security of sensitive data and its protection from unauthorised access is guaranteed. Hence for mining operations the GeODin platform presents a useful and relatively inexpensive range of tools, both to meet growing security concerns, whilst at the same time preventing economic down-time and so minimising financial losses. FOR MORE INFORMATION AND CONTACT:

FUGRO CONSULT GMBH Thomas Graf Fachbereichsleiter Bergbau/Infrastruktur Wolfener Strasse 36V12681 Berlin | GermanyTel.: +49 (0) 30 93 - 651 - 331Fax: +49 (0) 30 93 - 651 - 300eMail: T.Graf@fugro.deInternet: www.fugro.de

Fig. 4: Simplified flowchart showing the way of the data from the collection in the field to the web

based monitoring platform